Re: [PATCH v9 21/23] ima: Introduce securityfs file to activate an IMA namespace

[Stefan Berger <stefanb@xxxxxxxxxxxxx>]

On 1/26/22 09:31, Christian Brauner wrote:
> On Tue, Jan 25, 2022 at 05:46:43PM -0500, Stefan Berger wrote:
>
> Hm, I'd rather do something like (uncompiled, untested):
>
> +static ssize_t ima_write_active(struct file *filp,
> 				const char __user *buf,
> 				size_t count, loff_t *ppos)
> {
> 	struct ima_namespace *ns = &init_ima_ns;
> 	int err;
> 	unsigned int active;
> 	char *kbuf = NULL;
> 	ssize_t length;
>
> 	if (count >= 3)
> 		return -EINVAL;
>
> 	/* No partial writes. */
> 	if (*ppos != 0)
> 		return -EINVAL;
>
> 	if (ns_active(ns))
> 		return -EBUSY;
>
> 	kbuf = memdup_user_nul(buf, count);
> 	if (IS_ERR(kbuf))
> 		return PTR_ERR(kbuf);
>
> 	err = kstrtouint(kbuf, 10, &active);
> 	kfree(kbuf);
> 	if (err)
> 		return err;
>
> 	if (active != 1)
> 		return -EINVAL;
>
> 	atomic_set(&ns->active, 1);
> 	return count;
> }

Rearranged it to look lik this?

static ssize_t ima_write_active(struct file *filp,
                                const char __user *buf,
                                size_t count, loff_t *ppos)
{
        struct ima_namespace *ns = &init_ima_ns;
        unsigned int active;
        char *kbuf;
        int err;

        if (ns_is_active(ns))
                return -EBUSY;

        /* accepting '1\n' and '1\0' and no partial writes */
        if (count >= 3 || *ppos != 0)
                return -EINVAL;

        kbuf = memdup_user_nul(buf, count);
        if (IS_ERR(kbuf))
                return PTR_ERR(kbuf);

        err = kstrtouint(kbuf, 10, &active);
        kfree(kbuf);
        if (err)
                return err;

        if (active != 1)
                return -EINVAL;

        atomic_set(&ns->active, 1);
        return count;
}